1. Technical Field
The present invention relates to an electronic device that is worn on the wrist and has a built-in antenna for receiving radio signals that include time information and are transmitted from an external source.
2. Related Art
Electronic timepieces that have a wireless communication function have been available for some time. One use for this wireless communication function is to receive signals from a positioning information satellite, such as a GPS (Global Positioning System) satellite, and acquire the current time from the received satellite signal.
When a radio capability is rendered in a wristwatch as an example of an electronic timepiece with a radio function, an antenna that can provide satisfactory performance in a confined space is essential. See, for example, Japanese Unexamined Patent Appl. Pub. JP-A-2000-59241 and Japanese Unexamined Patent Appl. Pub. JP-A-2009-168656.
In JP-A-2000-59241, a C-shaped loop antenna with a dielectric substrate is disposed around the display unit, and the metal base of the wristwatch is used as a ground plate.
In JP-A-2009-168656, an unbalanced antenna is disposed around the perimeter of a dial located between the crystal and the movement of a wristwatch, and the dial is used as part of a ground plate.
A problem with the configurations taught in both JP-A-2000-59241 and JP-A-2000-59241 is that sufficient antenna performance cannot be assure. More particularly, the problem with the configurations taught in JP-A-2000-59241 and JP-A-2000-59241 is that the antenna and the ground plate (the metal base or the dial) are too close together, good reflection of RF signals from the ground plate is not achieved, and sufficient antenna performance cannot be obtained.